JP2008511794A - Low friction reciprocating pump - Google Patents

Abstract

  A reciprocating pump that pumps fluids, particularly fluids that tend to solidify when exposed to friction, such as UV inks. The pump has an internal transfer type chamber having an inlet, a discharge port, and a reciprocable plunger in the chamber. The plunger reciprocates through an axial passage in the housing at the end of the chamber. The passage is sized to receive the plunger with a clearance fit. The first and second seals are disposed in the shaft passage. The seals are annular in shape and extend between a plunger and a housing that are in sealing contact with each. The pump housing is away from the bearing in contact with the plunger or guiding its operation, and the sealing contact between the plunger and the seal is the only contact of the plunger in the housing.

Description

  The present invention relates to a reciprocating pump that pumps a fluid, and more particularly to a pump that extends the service life of the pump by reducing the frictional force applied to the fluid being pumped. A pump is described here for the first time as an application for pumping fluids that tend to solidify when exposed to frictional forces. However, pumps and sealing assemblies can be applied to effectively pump any type of fluid.

  Inks cured by ultraviolet (UV) energy are widely used in the printing and graphic display industries. Such inks are highly viscous and have inherent chemical properties that require special handling and pumping. The material composition of the ink contains monomers so that the ink solidifies when irradiated. It is an alternative to solvents as in conventional inks. Unfortunately, UV inks also react sensitively to mechanical shear stress (ie, frictional forces) that generate heat and cause the ink to solidify. Conventional transfer pumps expose UV ink to substantial frictional forces when pumped. As a result, the solidified polymer forms and accumulates in the pump. As a result, the pump is restrained and eventually fails. Of particular concern are gaps between close fitting parts that have relative motion. For example, a conventional pump has a reciprocating plunger. The reciprocating plunger is received in a fixed bearing or sleeve that guides movement and prevents plunger wander during reciprocating motion. The close fit sliding motion generates a high friction local area in a small gap between the plunger and the bearing or sleeve. UV ink reaching this gap tends to solidify. To prevent leakage, the plunger assembly must be sealed, exacerbating this problem.

  An object and feature of the present invention is to provide a fluid pump that exerts less frictional force on a fluid to be pumped, and to provide a fluid pump that effectively pumps a highly viscous fluid containing UV ink. Providing a fluid pump that is sealed to prevent fluid leakage and providing a fluid pump that is efficient, durable, and cost effective to assemble in use.

  In general, the reciprocating pump of the present invention is for pumping a fluid. The pump includes a pump housing having an internal transfer chamber with an inlet and an outlet, a longitudinal axis, and an opposing end. The plunger can reciprocate in the axial direction within the chamber. There is an axial passage at the end of the chamber in the housing through which the plunger reciprocates axially. The first and second annular seals in the axial passage are generally coaxial with the passage and away from the other longitudinal direction of the passage. Each seal is sized to sealingly contact the plunger. The pump housing is remote from the bearing that contacts the plunger or guides its operation. The plunger is not directly engaged with the housing and the hermetic contact between the plunger and the first and second seals is the only contact of the plunger within the housing.

  In another embodiment, the reciprocating pump of the present invention is for pumping a fluid. The pump includes a pump housing having an internal transfer chamber with an inlet and an outlet, a longitudinal axis, and an opposing end. The plunger can reciprocate in the axial direction within the chamber. There is an axial passage at the end of the chamber in the housing through which the plunger reciprocates axially. The shaft passage has at least a portion defining a minimum clearance area for the plunger in the housing. The minimum clearance area is sized to receive a plunger therethrough with a clearance fit. The plunger has an outer diameter D1, the minimum clearance region has an inner diameter D2, and D2 is at least about 0.015 inches greater than D1.

  In another embodiment, the reciprocating pump of the present invention is for pumping a fluid. The pump includes a pump housing having an internal transfer chamber with an inlet and an outlet, a longitudinal axis, and an opposing end. The plunger can reciprocate in the axial direction within the chamber. There is an axial passage at the end of the chamber in the housing through which the plunger reciprocates axially. The shaft passage has at least a portion defining a minimum clearance area for the plunger in the housing. The minimum clearance area of the axial passage has an axial length L1 of 1.0 inch or less.

  In yet another aspect, the reciprocating pump of the present invention is for pumping a fluid. The pump includes a pump housing having an internal transfer chamber with an inlet and an outlet, a longitudinal axis, and an opposing end. The housing includes a pump head, a cylinder attached to the head, and a gland attached to a head generally opposite the cylinder. The plunger can reciprocate in the axial direction within the chamber. There is an axial passage in the ground through which the plunger reciprocates axially. The first and second annular seals in the axial passage are generally coaxial with the passage and away from the other longitudinal direction of the passage. Each seal is sized for sealing contact with the plunger and has a generally U-shaped cross section with two opposing legs each in sealing contact with the plunger and the housing. The two legs of each seal are asymmetric. The axial passage includes an intermediate section between the seals that is sized to receive a plunger therethrough with a clearance fit. The inner shoulder is at the opposite end in the longitudinal direction of the middle section. Each seal is disposed proximate a respective shoulder of the shaft passage, and at least one seal is held by a screw nut. The pump housing is remote from the bearing that contacts the plunger or guides its operation. The plunger is not directly engaged with the housing and the hermetic contact between the plunger and the first and second seals is the only contact of the plunger within the housing.

  Other objects and features of the invention will be pointed out in part and will be set forth in part.

  Corresponding related reference characters indicate corresponding parts throughout the drawings.

  As shown in the drawings, and in particular in FIG. 1, the pump of the present invention for supplying fluid to an apparatus requiring fluid is generally indicated at 10. The pump 10 is used, for example, to pump ink from a supply container 12 (eg, a drum) to an injection tube of the printing machine 14. In one embodiment, the pump 10 is held on a companion plate 16 proximate the top surface of the fluid in the container 12. As the fluid moves, the plate 16 and the pump 10 move downward in the container 12 and the height of the upper surface of the fluid decreases. The pump 10 has a cylinder 20. The cylinder 20 is oriented vertically with the lower end submerged in the fluid of the container 12 in one embodiment. The lower end of the cylinder has an opening with an inlet 22 for receiving the fluid. A motor 24 is located above the pump to drive the pump, and a lateral discharge tube 26 extends from the pump to supply fluid to the printing press 14. Note that the pump 10 can have other arrangements and orientations without departing from the scope of the present invention.

  As shown in FIG. 2, the pump 10 includes a housing generally indicated by reference numeral 30. The housing includes a head 32 that is generally cylindrical and has a mounting flange 34. The cylinder 20 extends from the head 32 in a straight line with the head in the longitudinal direction. The flange 34 has a hole 36 for receiving a tie rod (not shown) for fixing the head 32 to the motor 24. A connector 38 and a connecting nut 39 are provided for operatively connecting the pump 10 to an electric drive shaft (not shown) of the motor 24. The discharge port 40 extends from the head 32 for connection to the discharge tube 26.

  As shown in FIG. 3, the head 32 and the cylinder 20 define an internal transfer chamber, generally indicated at 42, along the longitudinal axis C. The plunger 44 can reciprocate in the chamber 42 in the axial direction. In one embodiment, the plunger 44 is a cylinder having an outer diameter (radius) D1. In one embodiment, the outer surface of the plunger 44 includes a material that is smooth and suppresses friction with the fluid as it passes. A typical surface material is a series of nickel-base alloy coatings deposited by MAGNAPLATE HMF®, a patent-owned method of General Magnaplate Corporation, headquartered in Linden, NJ . The pump 10 has a first check valve (check valve) 46 at the inlet 22 in order to allow a one-way flow of the fluid into the chamber 42. The second check valve 48 at the discharge port 40 allows a one-way flow of fluid out of the chamber 42. In one embodiment, the first and second check valves 46, 48 have conventional round balls and corresponding pedestals. Such valves close quickly and reduce the possibility of small openings or gaps. A small opening or gap exposes the fluid to shear stress as it passes through the partially closed valve.

  The pump 10 is known to those skilled in the art as a “single-acting” type pump having a pump cycle that releases fluid only during a stroke in one direction of the plunger 44. During the upward stroke, the plunger 44 moves outward (upward in FIG. 3), the first check valve 46 opens, and the fluid is drawn into the chamber 42 through the inlet 22. The second check valve 48 is closed to block any discharge. During the downward stroke, the plunger 44 moves inward, the first check valve 46 closes, and the plunger transfers the fluid in the chamber 42 such that the fluid opens the second valve 48. The fluid is discharged through the discharge port 40 while the first check valve 46 is closed. Other forms of pump 10 do not depart from the scope of the present invention. In particular, the pump may be a “double acting” pump. In a “double acting” pump, fluid is pushed between two separate chambers in the pump and discharged during both the upper and lower stroke pump cycles.

  The pump housing 30 includes a gland 50 that is fixed (e.g., screwed) within a head 32 that is generally opposite the cylinder 20. The gland 50 defines an axial passage generally indicated by reference numeral 52 at one end (for example, the upper end) of the chamber 42, and the plunger 44 reciprocates in the axial direction in the axial passage. The ground 50 is shown in detail in FIGS. 5 and 6 alone. The gland has a generally cylindrical outer surface with a thread 54 in its upper portion. The upper part is provided with a hexagonal grip flange 56. To prevent leakage between the gland and the head 32, an annular groove 58 extends around the lower portion of the outer surface of the gland 50 to receive an O-ring seal 60, as shown in FIG.

  In the embodiment shown in FIG. 5, the axial passage 52 has an outer (upper) section 62 defined by a generally cylindrical first surface and an inner (lower) section of an outer section defined by a generally cylindrical second surface. ) And an inner (lower) section 66 defined by a generally cylindrical third surface. As shown, the middle section 64 has an inner diameter D2, the upper section 62 has an inner diameter D3 that is greater than D2, and the lower section 66 has an inner diameter D4 that is greater than D2, in the illustrated embodiment. , D3 and D4 are the same. As shown in FIG. 5 and described more fully below, the middle section 64 of the axial passage 52 has an axial length designated L1, and the upper and lower sections 62, 66 are designated L2 and L3, respectively. It has an axial length. Due to the relative size of the inner diameter of the upper, middle and lower sections of the passageway, the plunger 44 received in the gland 50 is more generally cylindrical in the middle section 64 than the surface of the upper and lower sections 62, 66. It is relatively close to the surface in the radial direction. The change in the inner diameter of the shaft passage 52 forms an outer (upper) flat annular shoulder 68 above the shaft passage and at the junction of the intermediate sections 62, 64. Similarly, an inner (lower) flat annular shoulder 70 is formed at the lower shaft passage and at the junction of the intermediate sections 66, 64. The gland 50 may vary continuously in diameter, may have a different arrangement of sections, may have more or less sections (including only one section of the same diameter), and / or The head may be formed integrally with the head without departing from the scope of the present invention.

  An annular groove 72 extends around the middle section 64 of the axial passage 52 and communicates with the lateral drain hole 74 for discharging fluid that may reach the axial passage. The hole 74 then communicates with a hole 76 (FIG. 4) in the head 32 of the pump 10. The plug 78 is screwed into the head hole 76 to stop ejection.

  As shown in FIG. 4, the first and second annular seals 80, 82 are disposed within the axial passage 52 substantially coaxially with respect to the axial passage and are separated from the other longitudinal direction of the axial passage. A first (upper) seal 80 is disposed in the upper section 62 of the axial passage proximate to the upper shoulder 68, and a second (lower) seal 82 is lower in the axial passage proximate to the lower shoulder 70. Located in section 66. Each of the seals is sized to enclose and make hermetic contact with the plunger 44. The upper seal 80 is removably held in the upper section 62 of the axial passage proximate the upper shoulder by a clamping nut 84 screwed into the gland 50. The lower seal 82 is removably retained in the lower section 66 of the axial passage by a retaining ring 85 received in the gland internal drain. The flat washer 86 is disposed between the ring 85 and the lower seal 82 to prevent damage to the seal. In one embodiment, each of the upper and lower seals 80, 82 is a cup seal, which has a generally U-shaped cross-sectional shape with a rectangular base and two recesses extending from the base and defining a recess between the legs. And opposite legs. The opposing legs are asymmetric and are configured to maintain hermetic contact with the respective surfaces of the gland 50 and the plunger 44. The radially inner leg tip 88 has a chamfered edge that includes a wiping surface in contact with the plunger 44. The seals 80, 82 are particularly towards the chamber 42 for effective sealing during the upper stroke of the plunger 44, where the plunger surface fluid tends to move out of the chamber with the plunger. Oriented by legs directed downward (FIG. 4 downward).

  In one embodiment, the first and second seals 80, 82 are substantially the same in size, material, and configuration. However, the seal can be changed without departing from the scope of the present invention. The seal is rigid and made of a suitable material that has high mechanical strength, flexibility, and elasticity beyond the pressure range. An exemplary material is an elastomer, such as polyurethane, having an indentation hardness (Shore A scale) of 87-97, more preferably an indentation hardness of about 92. In fact, an effective and commercially available seal is Disogrin®, which is an asymmetric piston U-cup seal manufactured by Simrit®, headquartered in Primouth, Michigan.

  In order to reduce friction, particularly friction resulting from shear stress applied on the fluid being pumped, the outer diameter D1 of the plunger 44 has a relatively relaxed clearance within the shaft passage 52. The size fits. In this regard, the inner diameter D2 of the narrowest section of the axial passage 52 (the intermediate section 64 of the illustrated embodiment) is much larger than the outer diameter D1 of the plunger 44, and the plunger shown in FIG. A clearance or gap G is defined around. In one embodiment, D2 is at least about 0.010 inches greater than D1, more preferably at least about 0.016 inches greater. This dimensional difference provides an average gap G of 0.005 inches, more preferably 0.008 inches, on each side of the plunger. In fact, the gap is wide enough and the shear stress on the fluid therein is insufficient to cause solidification of the UV ink. In one embodiment, D1 is 1.164 inches, D2 is 1.180 inches, and they have an average gap G of 0.008 inches on each side of the plunger and a diameter ratio D2 of 1.01 or greater. / D1 is provided.

  The relatively relaxed fit does not cause greater instability or “wobble” in the movement of the plunger 44 due to the sealing structure. The two seals 80, 82 function as bearings to guide and stabilize the operation of the plunger 44. The spaced apart sections of the seal in the upper and lower sections 62, 66 of the axial passage are proximate to the narrowest section 64 and provide effective communication for stabilizing the plunger 44. This arrangement avoids the need for a sleeve or bearing that results in increased friction. Further, if the UV ink fluid solidifies due to friction at the wiping surface 88 of the first and second seals 80, 82, the opposite effect is minimized by the relatively short axial length of the wiping surface, and each wiping At surface 88, the solidified ink is restricted to a narrow line.

  Friction is significantly suppressed by the relatively short longitudinal length of the narrowest section of the axial passage 52, ie, the intermediate section 64 of the illustrated embodiment. In one embodiment, the length L1 of this section is preferably in the range between about 0.4 inches and 1.0 inches, and more preferably about 0.9 inches. Therefore, the shear stress applied to the fluid is kept to a minimum in the range where the fluid leaks into this region. In practice, the length L1 is about 0.92 inches, providing a ratio of L1 to the plunger diameter D1 of about 0.79 (L1 / D1). The length L <b> 1 includes the length of the drain groove 72 that is wider than other portions of the intermediate section 64. When subtracting the length of the drain groove 72, the effective length L1 is about 0.73 inches, providing an effective ratio (L1 / D1) of about 0.63.

  As shown in FIG. 5, L1 is shorter than L2 but longer than L3. As an example, L1, L2, and L3 are 0.92 inches, 1.06 inches, and 0.58 inches, respectively. These dimensions may be changed.

  In addition, the friction is further reduced by the lack of valves and the suppression of shut-off in the discharge pipe 26 that supplies the fluid from the discharge port 40 of the pump chamber to the device 14 that requires the fluid. As a result, the fluid undergoes only minimal shear stress, and therefore less friction, thereby reducing fluid coagulation, resulting in more effective pumping and longer pump life.

  In view of the above, it will be appreciated that several objects of the present invention are realized and reach other advantages.

  In describing elements of the present invention or a preferred embodiment of the present invention, the articles "one", "its", and "above" mean that there are one or more elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

  Since various modifications can be made in the above configuration without departing from the scope of the present invention, all matters included in the above description are illustrative and limiting in meaning as shown in the accompanying drawings. It is to be interpreted as not.

1 is a schematic view of a system in which a pump of the present invention is pumping a fluid. It is a perspective view of a pump. It is a vertical sectional view of a pump. It is an expanded sectional view of FIG. It is a vertical sectional view of the gland of the pump. It is a perspective view of a ground.

Claims (13)

A reciprocating pump for pumping fluid,
A pump housing having an internal transfer chamber with an inlet and outlet, a longitudinal axis, and an opposing end;
A plunger capable of reciprocating along the axis in the chamber;
An axial passageway at one end of a chamber within the housing through which the plunger reciprocates axially;
Comprising first and second annular seals in the axial passage that are generally coaxial with the axial passage and away from the other longitudinal direction of the axial passage, each seal being in sealing contact with the plunger;
The pump housing is away from the bearing that contacts or guides the operation of the plunger, the plunger is not directly engaged with the housing, and the sealing contact between the plunger and the first and second seals Is a reciprocating pump characterized in that it is the only contact of the plunger in the housing.   The reciprocating pump of claim 1, wherein the axial passage comprises an intermediate section between the seals, the intermediate section being sized to receive a plunger therethrough with a clearance fit.   The reciprocating pump of claim 2, wherein the intermediate section of the axial passage defines a minimum clearance area for a plunger within the housing.   The reciprocating pump of claim 2, wherein the plunger has an outer diameter D1, the middle section of the shaft passage has an inner diameter D2, and the ratio of D2 to D1 is greater than 1.01.   The plunger has an outer diameter D1, the middle section of the shaft passage has a shaft length L1, and the ratio of L1 to D1 is in the range between 0.5 and 1.0. Item 3. A reciprocating pump according to item 2.   The axial passage has an internal shoulder at a longitudinally opposite end of the intermediate section, and each of the seals is disposed proximate to a respective shoulder in the axial passage. Reciprocating pump.   A screw nut received in the housing, the shaft passage having an internal shoulder therein, and one of the seals being held in a position proximate to the internal shoulder by the screw nut; The reciprocating pump according to claim 1.   The reciprocating pump of claim 1, wherein each seal has a generally U-shaped cross section with two opposing legs each in sealing contact with the plunger and the housing.   9. A reciprocating pump according to claim 8, wherein the two legs of each seal are asymmetric.   The housing includes a pump head, a cylinder attached to the head, and a gland attached to a head generally opposite the cylinder, wherein the axial passage is disposed in the gland. The reciprocating pump described. The pump is a single-acting pump and accepts fluid into the chamber through the inlet without simultaneously discharging from the outlet during the upper stroke,
The reciprocating pump according to claim 1, wherein the fluid is discharged from the chamber through the discharge port during the downward stroke.   The drain of claim 1, further comprising a drain, the drain comprising an annular groove in the axial passage for discharging fluid, the annular groove being located between the first and second seals. Reciprocating pump.   In a connection between a container that supplies fluid to the inlet of the chamber and a pipe that supplies fluid from the chamber outlet to a device that requires fluid, the tube is a valve between the outlet and the device. The reciprocating pump according to claim 1, wherein the reciprocating pump is not provided.

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